1. Field of the Invention
The present invention relates to a method of controlling a rear wheel steering apparatus, and more specifically, to a method of controlling an active rear wheel steering apparatus in which a rear wheel steering apparatus is controlled according to a mode selection condition of an automatic parking system.
2. Discussion of Related Art
A four-wheel steering system based on a rear wheel steering apparatus having a mechanical or hydraulic operation structure has been developed and produced by most car manufacturers based on a concept of a four-wheel steering system introduced in 1980s. However, as vehicle drivers feel sense of incongruity at the time of manipulation and ride comfort is low, spread of the system has failed.
However, a rear wheel steering system (RWS; Rear Wheel Steering) that has enhanced problems of an existing four-wheel steering system has been actively developed with a recently increasing development need for electrically powered chassis products for fuel consumption reduction, expansion of EV/HEV distribution, and safety improvement.
A development purpose of a four-wheel steering system, including a rear wheel steering system, is to improve mobility of a large vehicle by reducing a rotation radius at the time of low-speed turn through reverse phase control of the rear wheel steering system (relative to a front wheel steering direction), and improve stability of the vehicle by reducing a yaw-rate and a side-slip at the time of high-speed turn through in-phase control of the rear wheel steering system (relative to the front wheel steering direction).
Further, accordingly, a method of determining a rear wheel steering mode using information of various vehicles and calculating/controlling a rear wheel target steering angle is applied.
However, control of such a rear wheel steering system causes a change in behavior of the vehicle unlike an existing front wheel steering vehicle, and thus correction and variation of various calculation algorithms for an existing driver assistance system (DAS) based on a front wheel steering system are needed.
Particularly, an automatic parking system (Smart Parking Assist System; SPAS) is more sensitive to a change in a trace of a vehicle due to a rear wheel steering apparatus since a movement trace of a front wheel steering system-based body of the vehicle is calculated to perform a running plan for parking, and an error is often generated.
Therefore, there is a need for a method for solving the problems as described above.